1. Field of the Invention
The present invention relates to a laser diode and a method for producing the same, in particular, to a vertical-cavity surface emitting laser diode and a method for producing the same.
2. Description of the Related Art
For conventional vertical-cavity surface emitting laser (VCSEL) diode, the cavities of distributed Bragg reflectors (DBR) can be formed by epitaxial growth. In general, reflectivity of the DBR higher than 99% is required. To obtain such reflectivity, appropriate pair numbers of DBRs with appropriate refractive index deviation (Δn) are provided. For VCSEL devices of wavelength at 1,310 or 1,550 nm, only the InGaAsP/InP Bragg mirror grown on an active layer of InP series is considered. However, heat dissipation of the InGaAsP/InP mirror is poor and Δn thereof is too small when compared with GaAs/AlAs or dielectric Bragg mirrors. Therefore, lots of Bragg reflector pairs are associated to achieve desired reflectivity. As a result, complicated epitaxial processes including thousands of MBE or MOCVD during at least 4–8 hours is necessary. In addition, to maintain growth deviation of production less than 1% is very hard for manufacturing.
The above problems may be solved by applying direct wafer-bonding technology once or twice during manufacturing. For example, a laser diode of wavelength at 1,310 nm can be obtained by bonding an epitaxial structure to a GaAs substrate on which another epitaxial AlGaAs/GaAs DBR structure is grown. Such processes need an epitaxial system complying requirement of lattice matching which is not necessary for VCSEL epitaxial system. However, direct wafer-bonding needs to be performed at high temperature and through lattice alignment, which significantly limit production yields and increase manufacturing cost.
Therefore, it's desirable to find a laser diode and a method for producing the same to overcome the above disadvantages.